In manufacturing plants, bulk material is transported using various techniques. For instance, the material may be transported used using front end loaders, physical labor, conveyors, lifts, bucket elevators or pipes. One transportation approach that is in widespread use is to transport the material on a slightly inclined duct of fluidized air, referred to herein as an air slide.
An air slide is a system that uses the force of gravity to move the material. Air slides (also known as aeration conveyors) are used to convey powders using gravity by passing low-pressure air through a porous membrane media into the bed of the material being handled, resulting in the material becoming fluidized. Material movement is achieved by sloping the air slide to match the fluidized angle of repose of the material. At the correct slope, fluidized material will “flow” with the consistency of a liquid.
Air slides are typically used to transport material that generally has a granular consistency of flour, or powder. Examples of materials that are transported by air slide include raw meal and finished cement in cement plant operations. In many industries, it is beneficial to have measurements of the physical properties and composition of the material being transported. This information is used in various ways, for instance in verifying that the material is the correct blend or mixture of material, that the material has the correct material properties, or in using material properties to optimize the manufacturing process. Different measurements can be taken, including the elemental composition of the material, the molecular composition of the material, the granular size of the material, the reflectance of the material, the density of the material, and so forth. The exact measurements depend on the requirements for the application.
Various systems in the prior art have been developed to address quasi-real time assessment of moving material, primarily for non-air slide systems. For example, an in-line analyzer that is in wide spread use is a conveyor-belt analyzer using a technology called Prompt Gamma Neutron Activation Analysis (PGNAA). PGNAA uses thermal neutrons to measure the elemental composition of material on a conveyor belt. However, these systems work on conveyor belts and do not work on air slides. This is because both the low density of the material and the air slide geometrical differences render current technology unfavorable for PGNAA. An approach used on air slides is Near Infra-Red (NIR), but this is a surface measurement, and this measurement is not accurate because of inaccuracies due to changing characteristics of the material and layering in the material. To date, there is no highly accurate system for measuring fluidized material in an air slide.
Therefore, there has been a long-standing need in the industry for accurate, higher-performing air slide analyzers. Various details of such analyzers are elucidated in the following description.